This project will investigate pacing behavior in female mice at the neurochemical and behavioral levels. There has been extensive research examining pacing behavior in female rats. However them has not been any research examining pacing behavior in mice. With the emergence of knockout and transgenic models, our lab is now interested in using these models to study pacing behavior. We will use these models to add to the already existing data from pharmacological studies with rats. Female mice will be used to develop a pacing paradigm which will be used to assess the regulation of neurotransmitters on pacing behavior. This assessment will be done by using wild-type females which will be treated with serotonin agonists as well as knockout female mice. These knockout mice will be lacking serotonin and dopamine receptors. To assess the changes in neurochemical levels during pacing, biochemical techniques will be used such as high pressure liquid chromotography (HPLC). The results obtained from this project will further the understanding of pacing and its underlying mechanisms. We hope that this new animal model will stimulate interest in other regulatory mechanisms that underlie behavior.